Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$114.43	10.224%	$126.1293	$126.13	$126.15	$126.10
Purchase #2	$108.51	10.428%	$119.8254	$119.83	$119.85	$119.80
Purchase #3	$68.61	3.583%	$71.0683	$71.07	$71.05	$71.10
Purchase #4	$72.54	4.522%	$75.8203	$75.82	$75.80	$75.80
Purchase #5	$149.65	13.501%	$169.8542	$169.85	$169.85	$169.90
Purchase #6	$98.30	7.613%	$105.7836	$105.78	$105.80	$105.80
Purchase #7	$7.42	6.660%	$7.9142	$7.91	$7.90	$7.90
7 purchase totals =	$619.46		$676.3953	$676.39	$676.40	$676.40